Lubricating composition for a marine engine

ABSTRACT

The present invention relates to a lubricant composition for a marine engine, in particular for a four-stroke or two-stroke marine engine, comprising at least one base oil, at least one alkoxylated fatty amine, at least one hydrogenated styrene-isoprene copolymer and at least one detergent.

TECHNICAL FIELD

The present invention relates to the field of lubricants, and more particularly to the field of lubricants for a marine engine, in particular for a four-stroke or two-stroke marine engine, preferentially for a four-stroke marine engine. More particularly, the present invention relates to a lubricant composition comprising at least one base oil, at least one alkoxylated fatty amine, at least one hydrogenated styrene-isoprene copolymer and at least one detergent. The lubricant composition according to the invention simultaneously has good fuel economy properties and good engine cleanliness properties, in particular crankcase cleanliness. The present invention also relates to a method for reducing the fuel consumption of a vessel utilizing this lubricant composition.

The present invention also relates to a composition of the additives-concentrate type comprising at least one alkoxylated fatty amine, at least one hydrogenated styrene-isoprene copolymer and at least one detergent.

PRIOR ART

In the automotive field, due to environmental concerns, it is increasingly sought to reduce pollutant emissions and achieve fuel economies. The nature of engine lubricants for automobiles has an influence on these two phenomena. This is why so-called “fuel-eco” engine lubricants for automobiles have been developed. It is mainly the quality of the lubricant bases, alone or in combination with polymers improving the viscosity index and/or friction-modifying additives, which give the lubricant its “fuel-eco” properties. The fuel economies generated by means of “fuel-eco” engine lubricants are essentially achieved during cold starts, when the engine has not yet reached stabilized mode, and not at high temperature in stabilized mode. In general, gains in fuel efficiency in the NEDC (New

European Driving Cycle) according to European Directive 70/220/EEC are 5% at low temperature (urban cycle) and 1.5% at high temperature (extra-urban cycle) with average gains of 2.5%.

Now, in the field of marine lubricants, marine engines operate at a steady speed, and there are very few cold starts. Thus, the “fuel-eco” solutions suited to automobile engines are not suited to marine engines. In particular the fuel efficiency obtained in the automotive field cannot be obtained in the marine field.

Moreover, the formulation of a “fuel-eco” lubricant must not be detrimental to the lubricant's other performances. In particular, wear-resistance, demulsification, neutralizing ability, and engine cleanliness (piston and/or crankcase) should not be impaired.

Document FR 2 974 111 describes a cylinder lubricant for a two-stroke marine engine comprising at least one overbased detergent, at least one neutral detergent and at least one alkoxylated fatty amine having a BN (Base Number) determined according to the ASTM D-2896 standard ranging from 100 to 600 milligrams of potassium hydroxide per gram of amine. However, this document neither describes nor suggests the presence of a hydrogenated styrene-isoprene copolymer. Furthermore, this document gives no indication of fuel economy properties or heat-resistance properties under severe conditions, in particular in the presence of fuel.

It would therefore be desirable to have available a lubricant for a marine engine which allows satisfactory reductions in fuel consumption, while maintaining the lubricant's other performances, in particular engine cleanliness, more specifically the cleanliness of the crankcase.

It would also be desirable to have available a lubricant for a marine engine exhibiting good heat resistance under severe conditions of use, and more particularly in the presence of fuel. In fact, during the combustion of the fuel within the engine, combustion residues and unburned substances can pollute the lubricant and thus impair its heat resistance and detergent properties.

An objective of the present invention is to provide a lubricant composition that overcomes all or part of the aforementioned drawbacks.

Another objective of the invention is to provide a lubricant composition the formulation of which is easy to implement. Another objective of the present invention is to provide a lubrication method allowing fuel economies.

SUMMARY OF THE INVENTION

A subject of the invention is thus a lubricant composition for a 4-stroke or 2-stroke marine engine comprising:

-   -   a) at least one base oil,     -   b) at least one alkoxylated fatty amine,     -   c) at least one hydrogenated styrene-isoprene copolymer,     -   d) at least one detergent.

Surprisingly, the applicant found that it was possible to formulate lubricant compositions for marine engines making it possible to reduce the consumption of fuel, while maintaining or even improving engine cleanliness, in particular crankcase cleanliness, with respect to standard lubricant compositions for marine engines. This is made possible by means of a lubricant composition comprising at least one base oil, at least one alkoxylated fatty amine, at least one hydrogenated styrene-isoprene copolymer and at least one detergent.

Thus, the present invention makes it possible to formulate lubricant compositions for a 4-stroke or 2-stroke marine engine, making it possible to combine both engine cleanliness and gains in fuel economies.

Advantageously, the lubricant compositions according to the invention have an improved heat resistance under severe conditions, and more particularly in the presence of fuel.

Advantageously, the lubricant compositions according to the invention have an improved stability on storage, as well as a viscosity that varies very little or not at all over time.

In an embodiment, the invention relates to a lubricant composition for a 4-stroke or 2-stroke marine engine comprising:

-   -   a) at least one base oil,     -   b) at least one alkoxylated fatty amine,     -   c) at least one hydrogenated styrene-isoprene copolymer,     -   d) at least one detergent,     -   e) at least one dispersant.

In an embodiment, the lubricant composition essentially consists of:

-   -   a) at least one base oil,     -   b) at least one alkoxylated fatty amine,     -   c) at least one hydrogenated styrene-isoprene copolymer,     -   d) at least one detergent.

In an embodiment, the lubricant composition essentially consists of:

-   -   a) at least one base oil,     -   b) at least one alkoxylated fatty amine,     -   c) at least one hydrogenated styrene-isoprene copolymer,     -   d) at least one detergent,     -   e) at least one dispersant.

The invention also relates to a trunk piston engine oil (TPEO) comprising a lubricant composition as defined above.

By TPEO oil according to the invention, is meant any oily composition intended for lubricating 4-stroke marine engines, in particular the crankcase and cylinders.

The invention also relates to an cylinder oil comprising a lubricant composition as defined above.

By cylinder oil according to the invention, is meant any oily composition intended for lubricating the cylinders of 2-stroke marine engines.

The invention also relates to an system oil comprising a lubricant composition as defined above.

By system oil according to the invention, is meant any oily composition intended for lubricating the bottom part of 2-stroke marine engines, in particular the crankcase and crankshafts.

The invention also relates to the use of a lubricant composition as defined above for lubricating a 4-stroke or 2-stroke marine engine.

The invention also relates to the use of a lubricant composition as defined above for reducing the fuel consumption of a 4-stroke or 2-stroke marine engine.

The invention also relates to the use of at least one alkoxylated fatty amine in a lubricant composition for 2-stroke or 4-stroke marine engines comprising at least one base oil, at least one hydrogenated styrene-isoprene copolymer and at least one detergent, for improving the engine cleanliness of 4-stroke or 2-stroke marine engines, preferably the cleanliness of the crankcase of 4-stroke or 2-stroke marine engines.

The invention also relates to a composition of the additives-concentrate type comprising:

-   -   at least one alkoxylated fatty amine,     -   at least one hydrogenated styrene-isoprene copolymer,     -   at least one detergent.

The invention also relates to a method for lubricating a 4-stroke or 2-stroke marine engine comprising at least one step of bringing the engine into contact with a lubricant composition as defined above or obtained from the composition of the additives-concentrate type as described previously.

The invention also relates to a method for reducing the fuel consumption of 4-stroke or 2-stroke marine engines comprising at least one step of bringing a mechanical part of the engine into contact with a lubricant composition as defined above or obtained from the composition of the additives-concentrate type as defined above.

DETAILED DESCRIPTION

The percentages indicated below correspond to percentages of active material.

Alkoxylated Fatty Amine

The lubricant composition comprises at least one alkoxylated fatty amine. By alkoxylated fatty amine is meant, within the meaning of the present invention, a molecule comprising at least one amine function substituted with at least one alkyl group and at least one alkylene oxide group.

In an embodiment, the alkyl group can be chosen from the C₈-0₃₀ alkyl groups, preferably C₁₀-C₂₄, more preferentially C₁₂-C₂₂ and even more preferentially C₁₆-C₂₀.

In an embodiment, the alkylene oxide group can be chosen from the (C₂-C₁₀)-alkylene oxide groups, preferably (C₂-C₄)-alkylene and more preferentially (C₂-C₃)-alkylene.

According to the invention, the alkoxylated fatty amine is chosen from the alkoxylated fatty monoamines or the alkoxylated fatty polyamines.

In an embodiment, the alkoxylated fatty amine can be chosen from the alkoxylated fatty monoamines or the alkoxylated fatty diamines comprising one or more fatty aliphatic chains, preferably comprising a C₈-C₃₀ alkyl group, more preferentially a C₁₀-C₂₄ alkyl group, even more preferentially a C₁₂-C₂₂ alkyl group and advantageously a C₁₆-C₂₀ alkyl group.

These compounds, which have an intrinsic basicity and therefore an intrinsic BN, thus contribute to the BN of the lubricant compositions according to the invention. In an embodiment, the intrinsic BN of the alkoxylated fatty amines used in the lubricant composition according to invention, measured according to the ASTM D-2896 standard, can range from 100 to 600 milligrams of potassium hydroxide per gram of alkoxylated fatty amine, preferentially from 100 to 500 milligrams of potassium hydroxide per gram of alkoxylated fatty amine, more preferentially from 100 to 300 milligrams of potassium hydroxide per gram of alkoxylated fatty amine.

Alkoxylated fatty amine can be considered as a cationic-type surfactant the polar head of which is constituted by at least one nitrogen atom and by at least one oxygen atom provided by the alkoxylation and the lipophilic part of which is constituted by the fatty aliphatic chain(s).

Thus, in an embodiment, the polar head of the alkoxylated fatty amine can be constituted by amine functions a short distance from one another (typically separated by 2 to 3 carbon atoms), and preferentially restricted in number (typically one or two amine functions), and preferentially alkoxylated with a limited number of alkylene oxide functions, typically between 1 and 15, preferentially between 2 and 10, more preferentially between 3 and 7, even more preferentially between 3 and 4. Advantageously, the alkylene oxide group can be chosen from the (C₂-C₄)-alkylene oxide groups. This makes it possible to constitute a “compact” polar head, and therefore to confer a surfactant nature on these alkoxylated fatty amines.

The alkoxylated fatty amine can be obtained by known alkoxylation methods, for example described in the application FR 2 094 182, by bringing at least one fatty amine into contact with at least one alkylene oxide, at temperatures for example comprised between 100 and 200° C., in the presence of a basic catalyst such as NaOH, KOH or NaOCH₃. The starting fatty amine is mainly obtained from carboxylic acids. These acids are dehydrated in the presence of ammonia in order to produce nitriles, which then undergo catalytic hydrogenation in order to produce primary, secondary or tertiary amines.

The starting fatty amine is obtained from carboxylic acids, preferably from fatty acids. By fatty acid is meant, within the meaning of the invention, a carboxylic acid with a saturated or unsaturated aliphatic chain, comprising from 8 to 30 carbon atoms, preferably from 10 to 24 carbon atoms, more preferentially from 12 to 22 carbon atoms and even more preferentially from 16 to 20 carbon atoms.

In an embodiment, in order to obtain fatty amines, the starting fatty acids can be chosen from caprylic, pelargonic, capric, undecylenic, lauric, tridecylenic, myristic, pentadecylic, palmitic, margaric, stearic, nonadecylic, arachic, heneicosanoic, behenic, tricosanoic, lignoceric, pentacosanoic, cerotic, heptacosanoic, montanic, nonacosanoic, melissic, hentriacontanoic, laceroic acids or unsaturated fatty acids such as palmitoleic, oleic, erucic, nervonic, linoleic, α-linolenic, γ-linolenic, di-homo-y-linolenic, arachidonic, eicosapentaenoic or docosahexanoic acid.

In a preferred embodiment, the alkoxylated fatty amine is obtained from fatty acids comprising from 10 to 24 carbon atoms, preferably from 12 to 22 carbon atoms, more preferentially from 16 to 20 carbon atoms and even more preferentially from 16 to 18 carbon atoms.

In an embodiment, the fatty acids can originate from the hydrolysis of the triglycerides present in vegetable and animal oils, such as coconut, palm, olive, peanut, rapeseed, sunflower, soya, cotton, linseed oil or beef tallow. The natural oils may have been genetically modified so as to enrich their content of certain fatty acids, for example rapeseed oil or oleic sunflower oil.

Advantageously, the fatty amine used for preparing the alkoxylated fatty amine present in the lubricant composition according to the invention is obtained from natural, vegetable or animal resources. The treatments making it possible to produce fatty amines starting from natural oils can lead to mixtures of primary, secondary and tertiary monoamines, and polyamines. It is for example possible to use, for preparing the alkoxylated fatty amine present in the lubricant composition according to the invention, products containing, in variable proportions, all or some of the fatty amines corresponding to the following formulae:

R₁NH₂,

R₁—NH—R₂,

R₁—NHCH₂—R₂,

R₁—[NH(CH₂)₃]₂—NH₂,

R₁—[NH(CH₂)_(r)]_(s)—NH₂,

in which:

-   -   s represents an integer greater than or equal to 1,         preferentially ranging from 1 to 12, more preferentially from 1         to 5, advantageously from 1 to 2;     -   r represents an integer ranging from 2 to 3;     -   R₁ and R₂, identical or different, independently represent a         fatty chain originating from the fatty acid(s), originating from         the oil used as starting reagent.

A fatty monoamine or polyamine can contain several fatty chains originating from different fatty acids.

It is also possible to use these products in the purified form, predominantly containing a single type of amine, for example predominantly monoamines or predominantly diamines.

In an embodiment, a product constituted by primary monoamines of formula R₁NH₂ will be used, wherein R₁ can represent a plurality of fatty acids originating from a natural resource, for example tallow fat, or soya oil, or coconut oil, or (oleic) sunflower oil.

A product constituted by diamines of formula R₁—[NH(CH₂)₃]—NH₂, will thus be advantageously used, wherein R₁ can represent a plurality of fatty acids originating from a natural resource, for example tallow fat, or soya oil, or coconut oil, or (oleic) sunflower oil.

It is also possible to use purified products. For example, amines obtained from oleic acid are advantageously used, in particular primary monoamines of formula R₁NH₂ or diamines of formula R₁—[NH(CH₂)₃]—NH₂wherein R₁ is the fatty chain of oleic acid.

In an embodiment, the alkoxylated fatty amine present in the lubricant composition according to the invention is soluble in the base oil matrix.

The solubility of the alkoxylated fatty amine is initially due to its fatty chain(s). It is also all the more soluble as it comprises a limited number of alkylene oxide functions.

In an embodiment of the invention, the alkoxylated fatty amine is all the more soluble as it comprises no more than 15 alkylene oxide functions per amine molecule, preferably no more than 10 alkylene oxide functions, more preferentially no more than 7 alkylene oxide functions and even more preferentially no more than 4 alkylene oxide functions.

Moreover, the applicant found that an alkoxylated fatty amine where the nitrogen atoms are ternary (where there is no longer any N-H bond) is easier to solubilize.

In an embodiment of the invention, the alkoxylated fatty amine is chosen from the monoamines comprising a ternary nitrogen.

The alkoxylated fatty amine present in the lubricant composition according to the invention is therefore all the more effective, as it is well dispersed or even solubilized in the oil matrix.

Thus, in an embodiment, the alkoxylated fatty amine present in the lubricant composition according to the invention is not present in the form of an emulsion or a microemulsion, but in dispersed form, or even solubilized in the oil matrix.

Advantageously, the alkoxylated fatty amine comprises at least one aliphatic chain comprising at least 8 carbon atoms, preferably at least 10 carbon atoms, preferentially at least 12 carbon atoms, preferentially at least 14 carbon atoms, more preferentially at least 16 carbon atoms, advantageously from 16 to 20 carbon atoms.

In an embodiment of the invention, the lubricant composition according to the invention can comprise at least one alkoxylated fatty amine of formula (I):

in which:

-   -   R₃ represents an alkane-di-yl group comprising from 2 to 10         carbon atoms;     -   R₄ represents a linear or branched, saturated or unsaturated,         alkyl group comprising from 12 to 22 carbon atoms;     -   R₅ represents an alkane-di-yl group comprising from 1 to 10         carbon atoms;     -   m represents an integer ranging from 0 to 12;     -   n represents an integer ranging from 0 to 12;     -   p represents an integer ranging from 0 to 12;     -   q represents 0 or 1;     -   the sum m+n+p is strictly greater than 0, preferably 1<m+n+p<15,         preferentially 2<m+n+p<10, more preferentially 3<m+n+p<7,         advantageously 3<m+n+p<4.

In a preferred embodiment of the invention, the lubricant composition according to the invention can comprise at least one alkoxylated fatty amine of formula (I) in which:

-   -   R₃ represents an alkane-di-yl group comprising from 2 to 4         carbon atoms, preferably from 2 to 3 carbon atoms;     -   R₄ represents a linear or branched, saturated or unsaturated,         alkyl group comprising from 16 to 20 carbon atoms;     -   R₅ represents an alkane-di-yl group comprising from 2 to 4         carbon atoms;     -   m represents 0, 1, 2, 3, 4 or 5;     -   n represents 0, 1, 2, 3, 4 or 5;     -   p represents 0, 1, 2, 3, 4 or 5;     -   q represents 0 or 1;     -   the sum m+n+p represents an integer ranging from 1 to 15,         preferentially from 2 to 10, more preferentially from 3 to 7,         advantageously from 3 to 4.

Advantageously, the alkoxylated fatty amine is chosen from the compounds of formula (Ia):

in which:

-   -   R₃ represents an alkane-di-yl group comprising from 2 to 4         carbon atoms, preferably from 2 to 3 carbon atoms;     -   R₄ represents a linear or branched, saturated or unsaturated,         alkyl group comprising from 16 to 20 carbon atoms;     -   m represents 0, 1 or 2;     -   n represents 0, 1 or 2;     -   the sum m+n represents an integer ranging from 1 to 4,         preferably from 2 to 4.

Even more advantageously, the alkoxylated fatty amine is a compound of formula (la) in which:

-   -   R₃ represents a —(CH₂CH₂)— group,     -   R₄ represents a linear or branched mono-unsaturated alkyl group         comprising from 16 to 18 carbon atoms,     -   m represents 0, 1 or 2;     -   n represents 0, 1 or 2;     -   the sum m+n represents 2.

As an example of an alkoxylated fatty amine according to the invention, the product Ethomeen 0/12 marketed by the Akzo Nobel company can be mentioned.

In an embodiment of the invention, the content by weight of alkoxylated fatty amine ranges from 0.1 to 10%, preferably from 1 to 9%, advantageously from 2 to 8% with respect to the total weight of the lubricant composition.

Hydrogenated Styrene-Isoprene Copolymer

The lubricant composition according to the invention comprises at least one hydrogenated styrene-isoprene copolymer.

In an embodiment of the invention, the hydrogenated styrene-isoprene copolymer can be chosen from straight-chain hydrogenated styrene-isoprene copolymers or star-shaped hydrogenated styrene-isoprene copolymers (also called “star polymers”), preferably chosen from the star-shaped hydrogenated styrene-isoprene copolymers.

In an embodiment of the invention, the hydrogenated styrene-isoprene copolymer can be chosen from the hydrogenated styrene-isoprene block copolymers or the hydrogenated styrene-isoprene random copolymers.

Advantageously, the hydrogenated styrene-isoprene copolymer has a content of hydrogenated isoprene units, ranging from 50% to 98%, preferably from 60% to 98%, more preferentially from 70% to 97%, even more preferentially from 75% to 96% by mass, with respect to the mass of hydrogenated styrene-isoprene copolymer.

Advantageously, the hydrogenated styrene-isoprene copolymer has a content of styrene units ranging from 2% to 50%, preferably from 2% to 40%, more preferentially from 3% to 30%, even more preferentially from 4% to 25% by mass with respect to the mass of hydrogenated styrene-isoprene copolymer.

In an embodiment of the invention, the hydrogenated styrene-isoprene copolymer according to the invention has a weight-average molecular weight M_(w) ranging from 100,000 to 800,000 daltons, preferably from 200,000 to 700,000 daltons, more preferentially from 300,000 to 600,000 daltons, even more preferentially from 400,000 to 500,000 daltons.

In an embodiment of the invention, the hydrogenated styrene-isoprene copolymer according to the invention has a number-average molecular weight M_(n) ranging from 50,000 to 800,000 daltons, preferably from 75,000 to 600,000, more preferentially from 100,000 to 500,000, even more preferentially from 100,000 to 200,000.

In an embodiment of the invention, the hydrogenated styrene-isoprene copolymer according to the invention has a polydispersity index ranging from 1 to 4, preferably from 1.2 to 3.5, more preferentially from 1.5 to 3.5, even more preferentially from 2 to 3.

As examples of hydrogenated styrene-isoprene copolymers according to the invention, the products Shellvis 300 or Shellvis 301 marketed by the Infineum company can be mentioned.

In an embodiment of the invention, the content by weight of hydrogenated styrene-isoprene copolymer in the lubricant composition according to the invention is from 0.1% to 15% by mass, with respect to the total mass of the lubricant composition, preferably from 0.1% to 10%, more preferentially from 0.2% to 5%, advantageously from 0.5 to 2%. By this quantity is meant a quantity of active polymer material. In fact, the hydrogenated styrene-isoprene copolymer used in the context of the present invention can be presented in the form of a dispersion in a mineral or synthetic oil, and more particularly in an oil of Group I according to the API classification.

Detergent

The lubricant composition according to the invention comprises at least one detergent.

In an embodiment, the detergent used in the lubricant composition according to the invention can be chosen from the detergents commonly used in lubricant compositions.

The detergent commonly used in the formulation of lubricant compositions is typically an anionic compound comprising a long lipophilic hydrocarbon-containing chain and a hydrophilic head. The associated cation is typically a metallic cation of an alkali or alkaline-earth metal.

In an embodiment of the invention, the detergent can be chosen from the alkali or alkaline-earth metal salts of carboxylic acids, sulphonates, salicylates, naphthenates, and phenates alone or in a mixture. The detergents are named according to the nature of the hydrophobic chain, carboxylate, sulphonate, salicylate, naphthenate or phenate.

In an embodiment of the invention, the alkali and alkaline-earth metals are chosen from calcium, magnesium, sodium or barium, preferentially calcium.

In an embodiment of the invention, the detergent can be chosen from the non-overbased (or neutral) detergents or overbased detergents.

The term non-overbased or “neutral” detergents is used when the metallic salts contain the metal in an approximately stoichiometric quantity with respect to the anionic group(s) of the detergent.

The term overbased detergents is used when the metal is in excess (in a quantity greater than the stoichiometric quantity with respect to the anionic group(s) of the detergent). The metal in excess providing the overbased character to the detergent is presented in the form of metallic salts that are insoluble in oil. The overbased detergents are presented in the form of micelles. These detergents constituted by metallic salts that are soluble in oil thus stabilize the insoluble metallic salts, by maintaining them in suspension in the lubricant composition.

These micelles can contain one or more types of insoluble metallic salts, stabilized by one or more types of detergents. The overbased detergents will be referred to as of mixed type if the micelles comprise several types of detergents which differ from each other in the nature of their hydrophobic chain.

Advantageously, the detergent is chosen from the alkali and alkaline-earth metal salicylates, carboxylates, sulphonates and/or phenates, alone or in a mixture, preferentially from the calcium salicylates, sulphonates and/or phenates.

The detergent present in the lubricant composition according to the invention can also be chosen from the non-metallic and non-overbased detergents.

In an embodiment, the detergent is chosen from the amine- and borate-containing compounds. In an embodiment, the detergent can be an amine- and borate-containing compound originating from the reaction between an alkylated derivative of salicylic acid and a dialkoxylated amine, in the presence of boric acid.

The detergent can thus be obtained by implementation of the method described in document WO 2007/081494.

In an embodiment, the detergent can be chosen from the amine- and borate-containing derivatives of salicylic acid.

In a preferred embodiment, the detergent is a compound of formula (II)

in which:

-   -   R₅ represents a linear or branched alkyl group comprising from 2         to 30 carbon atoms, preferably from 5 to 20 carbon atoms,         advantageously from 15 to 20 carbon atoms;     -   R₆ represents a linear or branched alkyl group comprising from 2         to 30 carbon atoms, preferably from 5 to 20 carbon atoms,         advantageously from 12 to 20 carbon atoms;     -   R₇ represents a linear or branched alkyl group comprising from 2         to 30 carbon atoms, preferably from 5 to 20 carbon atoms,         advantageously from 12 to 20 carbon atoms;     -   r is an integer ranging from 1 to 100.

Advantageously, the R₆ and R₇ groups are identical and both represent a linear or branched alkyl group comprising from 12 to 20 carbon atoms.

In a preferred embodiment of the invention, the detergent is chosen from alkali or alkaline-earth metal salicylates or phenates, alone or in a mixture.

Advantageously, the detergent is chosen from calcium salicylates or calcium phenates, alone or in a mixture.

In another preferred embodiment, the detergent is a mixture of an alkali or alkaline-earth metal salicylate and of a compound of formula (II).

In another preferred embodiment, the detergent is a mixture of an alkali or alkaline-earth metal phenate and of a compound of formula (II).

In another preferred embodiment, the detergent is a mixture of an alkali or alkaline-earth metal phenate, an alkali or alkaline-earth metal salicylate and a compound of formula (II).

Advantageously, the combination of a compound of formula (II) and an alkali or alkaline-earth metal phenate and/or salicylate makes it possible to enhance the heat resistance of the lubricant composition according to the invention, in particular under severe conditions, and more particularly in the presence of fuel.

In an embodiment of the invention, the content by weight of detergents in the lubricant composition according to the invention ranges from 1% to 20%, preferentially from 1% to 15%, more preferentially from 2% to 10% with respect to the total weight of the lubricant composition.

The BN of the lubricant compositions according to the present invention is provided by the alkoxylated fatty amine and by the detergent(s).

The BN value of the lubricant compositions according to the present invention, measured according to the ASTM D-2896 standard, can vary from 5 to 100 mg of KOH/g of lubricant composition, preferably from 7 to 80 mg of KOH/g of lubricant composition, more preferentially from 10 to 60 mg of KOH/g of lubricant composition. The BN value is chosen depending on the conditions of use of the lubricant compositions and in particular according to the sulphur content of the fuel used.

Thus for fuels with a high sulphur content (in the range of 0.2% to 4.5% by weight), the BN value is significant and preferably comprised between 20 and 80 mg of KOH/g of lubricant composition, more preferentially between 30 and 65 mg of KOH/g of lubricant composition. For fuels with a low sulphur content (in the range of 0.05% to 0.2% by weight), the BN value is low and preferably comprised between 5 and 20 mg of KOH/g of lubricant composition, more preferentially between 10 and 15 mg of KOH/g of lubricant composition.

Base Oils

In general, the base oils used for the formulation of lubricant compositions according to the invention can be chosen from oils of mineral, synthetic or vegetable origin as well as mixtures thereof.

The mineral or synthetic oils generally used in the marine engine oil application belong to one of the classes defined in the API classification as summarized in the table below.

Saturates Sulphur Viscosity index content content (VI) Group I Mineral oils <90% >0.03% 80 ≦ VI < 120 Group II ≧90% ≦0.03% 80 ≦ VI < 120 Hydrocracked oils Group III ≧90% ≦0.03% ≧120 Hydro-isomerized oils Group IV Poly-alpha-Olefins (PAO) Group V Other bases not included in bases of Groups I to IV

The mineral oils of Group I can be obtained by distillation of selected naphthenic or paraffinic crude oils, then by purification of these distillates by methods such as solvent extraction, solvent or catalytic dewaxing, hydrotreating or hydrogenation. The mineral bases of Group I are for example the bases called Neutral Solvent (such as for example 150NS, 330NS, 500NS or 600NS) or Brightstock.

The oils of Groups II and III are obtained by more stringent purification methods, for example a combination of hydrotreating, hydrocracking, hydrogenation and catalytic dewaxing. Examples of synthetic bases of Groups IV and V include the poly-alpha olefins, polybutenes, polyisobutenes and alkylbenzenes.

These base oils can be used alone or in a mixture. A mineral oil can be combined with a synthetic oil.

In a preferred embodiment of the invention, the lubricant base oil is chosen from the base oils of Group I or Group II, alone or in a mixture.

In an embodiment of the invention, the lubricant composition according to the invention can be characterized by a viscosity grade of SAE-20, SAE-30, SAE-40, SAE-50 or SAE-60 according to the SAEJ300 classification.

Grade 20 oils have a kinematic viscosity at 100° C. comprised between 5.6 and 9.3 cSt.

Grade 30 oils have a kinematic viscosity at 100° C. comprised between 9.3 and 12.5 cSt.

Grade 40 oils have a kinematic viscosity at 100° C. comprised between 12.5 and 16.3 cSt.

Grade 50 oils have a kinematic viscosity at 100° C. comprised between 16.3 and 21.9 cSt.

Grade 60 oils have a kinematic viscosity at 100° C. comprised between 21.9 and 26.1 cSt.

The kinematic viscosity is measured according to the ASTM D7279 standard at 100° C.

In a preferred embodiment, the lubricant composition according to the invention has a kinematic viscosity measured according to the ASTM D7279 standard at 100° C. comprised between 5.6 and 26.1 cSt, preferably between 9.3 and 21.9 cSt, more preferentially between 12.5 and 16.3 cSt.

In an embodiment of the invention, the content by weight of base oil in the lubricant composition according to the invention is from 30% to 90%, preferably from 40% to 90%, more preferentially from 50% to 85%, advantageously from 65 to 85% with respect to the total weight of the lubricant composition.

In an embodiment, the lubricant composition is not presented in the form of an emulsion.

In an embodiment, the lubricant composition according to the invention is presented in the form of an anhydrous composition.

Other Additives

In an embodiment, the lubricant composition according to the invention can also comprise a dispersant.

The dispersants are well-known additives used in the formulation of lubricant compositions, in particular for application in the marine field. Their first role is to keep in suspension the particles originally present or appearing in the lubricant composition during its use in the engine. They prevent their agglomeration by acting on the steric hindrance. They can also have a synergistic effect on the neutralization.

The dispersants used as lubricant additives typically contain a polar group, associated with a relatively long hydrocarbon-containing chain, generally containing from 50 to 400 carbon atoms. The polar group typically contains at least one nitrogen, oxygen or phosphorus element.

In an embodiment of the invention, the dispersant can be chosen from the succinic acid derivatives. By succinic acid derivatives is meant, within the meaning of the invention, the succinic acid esters or succinic acid amide esters.

Preferably, the dispersant is chosen from the compounds comprising at least one succinimide group.

These compounds can be then treated with various compounds, in particular sulphur, oxygen, formaldehyde, carboxylic acids and compounds containing boron or zinc in order to produce, for example, borated succinimides or zinc-blocked succinimides.

In a preferred embodiment of the invention, the dispersant is chosen from the borated compounds comprising at least one succinimide group.

In a preferred embodiment of the invention, the dispersant can be chosen from the borated compounds comprising at least one substituted succinimide group or the borated compounds comprising at least two substituted succinimide groups, the succinimide groups being able to be linked at their vertex bearing a nitrogen atom, by a polyamine group.

By substituted succinimide group within the meaning of the present invention, is meant a succinimide group at least one of the vertices of which is substituted with a hydrocarbon group comprising from 8 to 400 carbon atoms.

Advantageously, the dispersant is chosen from the borated compounds comprising at least one succinimide group substituted with a polyisobutene group.

Advantageously, the dispersant is chosen from the borated compounds comprising at least two succinimide groups each substituted with a polyisobutene group.

More advantageously, the dispersant is chosen from the borated compounds comprising at least two succinimide groups each substituted with a polyisobutene group and characterized by:

-   -   A number molecular weight of the polyisobutene greater than 2000         Daltons, preferably ranging from 2000 to 5000 Daltons,         advantageously from 2000 to 3000 Daltons,     -   A content by mass of the element boron greater than or equal to         0.35% with respect to the total mass of the dispersant.

As an example of a dispersant additive according to the invention, the product T161B from the Tianhe company can be mentioned.

Mannich bases, obtained by polycondensation of phenols substituted with alkyl groups, formaldehyde and primary or secondary amines, can also be used as dispersants in the lubricant composition according to the invention.

In an embodiment of the invention, the content by weight of dispersant is at least 0.1%, preferably from 0.1% to 10%, advantageously from 1% to 6% with respect to the total weight of the lubricant composition.

In addition to the compounds as described above, the lubricant composition according to the invention can comprise at least one additional additive, in particular chosen from those commonly used by a person skilled in the art.

In an embodiment, the additional additive can be chosen from anti-wear additives, antioxidants, additional polymers improving the viscosity index, pour point improvers, anti-foaming agents, thickeners and mixtures thereof.

The anti-wear additives protect the friction surfaces by the formation of a protective film adsorbed on these surfaces. A great variety of anti-wear additives exists. The phosphorus- and sulphur-containing additives, such as the metallic alkylthiophosphates, in particular the zinc alkylthiophosphates, and more specifically the zinc dialkyldithiophosphates (or ZnDTP) can thus be mentioned. The alkyl groups of these zinc dialkyldithiophosphates, preferentially comprise from 1 to 18 carbon atoms. The amine phosphates, the polysulphides, in particular the sulphur-containing olefins, are also commonly used anti-wear additives. Anti-wear additives of the nitrogen- and sulphur-containing type, such as for example metallic dithiocarbamates, in particular molybdenum dithiocarbamate are also encountered. The preferred anti-wear additive is ZnDTP.

The content by weight of anti-wear additive in the lubricant according to the invention is from 0.1% to 5%, preferably from 0.2% to 4%, more preferentially from 0.2% to 2% with respect to the total weight of the lubricant composition.

By additional polymers improving the viscosity index according to the invention, is meant any polymer improving the viscosity index other than the hydrogenated styrene-isoprene copolymer according to the invention.

These additional polymers improving the viscosity index can be chosen from the polymer esters, olefin copolymers (OCP) or polymethacrylates (PMA).

The anti-foaming additives can be chosen from the polar polymers such as polymethylsiloxanes or polyacrylates.

These additives are generally present in a content by weight of 0.01 to 3% with respect to the total weight of the lubricant composition.

A subject of the invention is also a lubricant composition for a 4-stroke or 2-stroke marine engine comprising:

-   -   from 30 to 90% of at least one base oil,     -   from 0.1 to 10% of at least one alkoxylated fatty amine,     -   from 0.1 to 15% of at least one hydrogenated styrene-isoprene         copolymer,     -   from 1 to 20% of at least one detergent.

In an embodiment, the lubricant composition essentially consists of:

-   -   from 30 to 90% of at least one base oil,     -   from 0.1 to 10% of at least one alkoxylated fatty amine,     -   from 0.1 to 15% of at least one hydrogenated styrene-isoprene         copolymer,     -   from 1 to 20% of at least one detergent.

All the characteristics and preferences presented for the base oil, the alkoxylated fatty amine, the hydrogenated styrene-isoprene copolymer and the detergent also apply to the above lubricant compositions.

A subject of the invention is also a lubricant composition for a 4-stroke or 2-stroke marine engine comprising:

-   -   from 30 to 90% of at least one base oil,     -   from 0.1 to 10% of at least one alkoxylated fatty amine,     -   from 0.1 to 15% of at least one hydrogenated styrene-isoprene         copolymer,     -   from 1 to 20% of at least one detergent,     -   from 0.1 to 10% of at least one dispersant.

In an embodiment, the lubricant composition essentially consists of:

-   -   from 30 to 90% of at least one base oil,     -   from 0.1 to 10% of at least one alkoxylated fatty amine,     -   from 0.1 to 15% of at least one hydrogenated styrene-isoprene         copolymer,     -   from 1 to 20% of at least one detergent,     -   from 0.1 to 10% of at least one dispersant.

All the characteristics and preferences presented for the base oil, the alkoxylated fatty amine, the hydrogenated styrene-isoprene copolymer, the detergent and the dispersant also apply to the above lubricant compositions.

The lubricant composition according to the invention can be used in 4-stroke or 2-stroke marine engines.

In a preferred embodiment, the lubricant composition is used in high-speed or medium-speed 4-stroke engines, which operate with distillates and bunker fuels or heavy fuel respectively. The fuel economy applies in particular to the distillates used in high-speed 4-stroke engines. High-speed 4-stroke engines are used for the propulsion of small vessels and as electricity generating units on board larger vessels. Medium-speed 4-stroke engines are used for the propulsion of numerous vessels, such as cargo ships, tankers, ferries, or even certain container ships. They can moreover be used as electricity generating units on board large vessels or in diesel electricity generating stations.

In particular, the lubricant composition is appropriate for 4-stroke engines as trunk piston oil (TPEO).

In particular, the lubricant composition is appropriate for 2-stroke engines as system oil or cylinder oil.

Thus a subject of the invention is also the use of a lubricant composition as defined above for the lubrication of 4-stroke or 2-stroke marine engines.

In a preferred embodiment, the invention relates to the use of a lubricant composition as defined above for the lubrication of 4-stroke marine engines. All the characteristics and preferences presented for the lubricant composition apply to the above use.

The invention also relates to the use of a lubricant composition as defined above for reducing the fuel consumption of 4-stroke or 2-stroke marine engines.

In a preferred embodiment, the invention relates to the use of a lubricant composition as defined above for reducing the fuel consumption of 4-stroke marine engines.

The reduction in fuel consumption is in particular evaluated by testing on a marine engine test bench or by evaluation of the coefficient of traction on a machine, in particular on a mini traction machine (MTM).

All the characteristics and preferences presented for the lubricant composition apply to the above use.

The invention also relates to the use of at least one alkoxylated fatty amine in a lubricant composition for 2-stroke or 4-stroke marine engines comprising at least one base oil, at least one hydrogenated styrene-isoprene copolymer and at least one detergent, for improving the engine cleanliness of 4-stroke or 2-stroke marine engines, preferably the cleanliness of the crankcase of 4-stroke or 2-stroke marine engines.

The engine cleanliness is in particular evaluated by the continuous ECBT and continuous fuel ECBT methods.

All the characteristics and preferences presented for the base oil, the alkoxylated fatty amine, the hydrogenated styrene-isoprene copolymer and the detergent also apply to the above use.

The compounds as defined above contained in the lubricant composition according to the invention, and more particularly the alkoxylated fatty amine, the hydrogenated styrene-isoprene copolymer, the detergent and optionally the dispersant, can be incorporated in the lubricant composition as separate additives, in particular by the separate addition of the latter to the base oils.

However, they can also be incorporated in an additives concentrate for a marine lubricant composition.

Thus, a subject of the invention is also a composition of the additives-concentrate type comprising:

-   -   at least one alkoxylated fatty amine,     -   at least one hydrogenated styrene-isoprene copolymer,     -   at least one detergent.

All the characteristics and preferences presented for the alkoxylated fatty amine, the hydrogenated styrene-isoprene copolymer and the detergent also apply to the above composition.

A subject of the invention is also a composition of the additives-concentrate type comprising:

-   -   at least one alkoxylated fatty amine,     -   at least one hydrogenated styrene-isoprene copolymer,     -   at least one detergent,     -   at least one dispersant.

All the characteristics and preferences presented for the alkoxylated fatty amine, the hydrogenated styrene-isoprene copolymer, the detergent and the dispersant also apply to the composition above.

In an embodiment, the composition of the additives-concentrate type can comprise:

-   -   from 0.5 to 50% of at least one alkoxylated fatty amine,     -   from 1.5 to 25% of at least one hydrogenated styrene-isoprene         copolymer,     -   from 2.5 to 25% of at least one detergent; % by weight with         respect to the total weight of the composition of the         additives-concentrate type.

In another embodiment, the composition of the additives-concentrate type can comprise:

-   -   from 0.5 to 50% of at least one alkoxylated fatty amine,     -   from 1.5 to 25% of at least one hydrogenated styrene-isoprene         copolymer,     -   from 2.5 to 25% of at least one detergent,     -   from 2 to 40% of at least one dispersant; % by weight with         respect to the total weight of the composition of the         additives-concentrate type.

In an embodiment of the invention, at least one oil base can be added to the composition of the additives-concentrate type according to the invention in order to obtain a lubricant composition according to the invention.

Another subject of the invention relates to a method for lubricating a 4-stroke or 2-stroke marine engine, said method comprising at least one step of bringing the engine into contact with the lubricant composition as described previously or obtained from the composition of the additives-concentrate type as described previously.

All the characteristics and preferences presented for the lubricant composition or for the composition of the additives-concentrate type also apply to the lubrication method according to the invention.

Another subject of the invention relates to a method for reducing the fuel consumption of a 4-stroke or 2-stroke marine engine comprising at least one step of bringing a mechanical part of the engine into contact with the lubricant composition as defined above or obtained from the composition of the additives-concentrate type as defined above.

All the characteristics and preferences presented for the lubricant composition or for the composition of the additives-concentrate type also apply to the method for reducing the fuel consumption according to the invention.

The different subjects of the present invention and implementation thereof will be better understood on reading the following examples. These examples are given by way of indication, without being limitative.

EXAMPLE 1 Evaluation of the Heat-Resistance Properties of Lubricant Compositions According to the Invention

The heat resistance of lubricant compositions according to the invention is evaluated by implementation of the continuous ECBT test, thus simulating the engine cleanliness in the presence of such compositions.

To this end, different lubricant compositions were prepared from the following compounds:

-   -   Group I base oils, in particular referred to as Neutral Solvent         150NS, 330NS or 600NS, with a viscosity at 40° C. of 30 cSt, 66         cSt and 120 cSt respectively, measured according to the ASTM         D7279 standard,     -   a hydrogenated styrene-isoprene (HSI) copolymer having a         star-shaped conformation, diluted to 9% of active material in a         Group I base oil (Shellvis 301 marketed by the Infineum         company),     -   an ethoxylated oleic monoamine (Ethomeen O/12 marketed by the         AKZO NOBEL company),     -   an overbased detergent based on calcium phenates and calcium         salicylates and dispersed at 25% of active material in an oil,     -   a non-metallic and non-overbased detergent of formula (II) as         described previously in which:     -   R₅ represents a C₁₈H₃₇ group,     -   R₆ and R₇ both represent a C₁₆H₃₃ group,     -   r represents an integer ranging from 1 to 100,     -   a dispersant of the borated compound type comprising at least         one succinimide group substituted with a polyisobutene group         (T161B marketed by the Tianhe company)     -   an anti-wear additive of the zinc dithiophosphate type,     -   a silicone-containing anti-foaming additive.

The different lubricant compositions L₁ to L₅ are described in Table I; the percentages indicated correspond to percentages by mass.

TABLE I L₁ L₂ L₃ L₄ L₅ (compar- (compar- (inven- (inven- (inven- Compositions ative) ative) tion) tion) tion) Base oils 78.28 83.08 77.58 75.88 76.38 Anti-wear 0.5 0.5 0.5 0.5 0.5 additive Anti-foaming 0.02 0.02 0.02 0.02 0.02 additive Overbased 13.70 8 8 8 8 detergent Hydrogenated 7.5 7.5 7.5 7.5 styrene- isoprene copolymer Ethoxylated 6.4 6.4 6.4 3.2 oleic monoamine Non-metallic 4.4 and non- overbased detergent Dispersant 2 1.7

The content of 13.70% of overbased detergent in the composition L₁ corresponds to a content of 8% of overbased detergent in the presence of ethoxylated oleic monoamine, this content making it possible to obtain a stable composition and being able to be evaluated.

The physico-chemical characteristics of compositions L₁ to L₅ are described in Table II.

TABLE II L₁ L₂ L₃ L₄ L₅ (compar- (compar- (inven- (inven- (inven- Compositions ative) ative) tion) tion) tion) Kinematic 13.68 13.61 13.98 14.36 14.11 viscosity in mm²/s (measured at 100° C. according to the ASTM D7279 standard) Kinematic 101.6 137.7 107 108.3 103 viscosity in mm²/s (measured at 40° C. according to the ASTM D7279 standard) Viscosity 135 93.6 131.6 135 139.3 index (VI)

Composition L₂ comprises no hydrogenated styrene-isoprene copolymer, which explains the drop in the viscosity index and the increase in kinematic viscosity.

The heat resistance of compositions L₁ to L₅ was therefore evaluated by means of the continuous ECBT test, whereby the mass of deposits (in mg) generated under defined conditions is measured. The lower this mass, the better the heat resistance and therefore the better the engine cleanliness.

This test simulates an engine piston heated to a high temperature, onto which the lubricant originating from the crankcase is sprayed.

The test utilizes aluminium beakers which simulate the shape of pistons. These beakers were placed in a glass container maintained at a controlled temperature of the order of 60° C.

The lubricant was placed in these containers, themselves equipped with a wire brush, partially immersed in the lubricant. This brush was rotated at a speed of 1000 rpm, which creates a spray of lubricant onto the lower surface of the beaker. The beaker was maintained at a temperature of 310° C. by an electrical heating resistance, regulated by a thermocouple.

In the continuous ECBT test, the test had a duration of 12 hours and the spraying of lubricant was continuous. This procedure makes it possible to simulate the formation of deposits in the piston-ring assembly. The result is the weight of deposits measured on the beaker.

A detailed description of this test is given in the publication entitled “Research and Development of Marine Lubricants in ELF ANTAR France—The relevance of laboratory tests in simulating field performance” by Jean-Philippe ROMAN, MARINE PROPULSION CONFERENCE 2000—AMSTERDAM—29-30 MARCH 2000.

The results are summarized in Table III below.

TABLE III L₁ L₂ L₃ L₄ L₅ (compar- (compar- (inven- (inven- (inven- Compositions ative) ative) tion) tion) tion) Continuous 506 172 350 286 386 ECBT (mg)

The results show that the compositions according to the invention have good heat resistance and thus make it possible to improve engine cleanliness.

It is to be noted that the lubricant compositions have improved heat resistance with respect to lubricant compositions comprising a hydrogenated styrene-isoprene copolymer alone.

It is also to be noted that the lubricant compositions according to the invention retain good heat resistance, despite the presence of the hydrogenated styrene-isoprene copolymer which is known for its very poor heat resistance.

EXAMPLE 2 Evaluation of the Heat-Resistance Properties of Lubricant Compositions According to the Invention under Severe Conditions

The heat resistance of lubricant compositions according to the invention under severe conditions in the presence of fuel is evaluated by the implementation of the continuous ECBT fuel test, thus simulating engine cleanliness in the presence of such compositions under severe conditions.

As for the continuous ECBT test, the continuous ECBT fuel test simulates an engine piston heated to high temperature, onto which the lubricant originating from the crankcase is sprayed.

The lubricant has been polluted with heavy fuel (2.5% m/m with respect to the quantity of lubricant) in order to simulate the pollution of an engine lubricant with residues and unburned substances from the fuel following combustion.

The equipment is identical to that of the continuous ECBT test of Example 1.

The lubricant mixed with the heavy fuel was placed in the glass container maintained at a temperature of approximately 60° C. The metal beaker was maintained at a temperature of 250° C., the test had a duration of 12 hours and the spraying of the lubricant was continued throughout these 12 hours.

The results are described in Table IV and correspond to the weight of deposit measured on the metal beaker. The lower this mass, the better the heat resistance and therefore the better the engine cleanliness under severe conditions.

TABLE IV L₁ L₂ L₃ L₄ L₅ (compar- (compar- (inven- (inven- (inven- Compositions ative) ative) tion) tion) tion) Continuous 223 43 147 129 124 fuel ECBT (mg)

The results show that the compositions according to the invention have good heat resistance, and thus make it possible to retain good engine cleanliness, even under severe conditions, in particular in the presence of heavy fuel.

It is to be noted that the lubricant compositions have improved heat resistance under severe conditions, with respect to lubricant compositions comprising a hydrogenated styrene-isoprene copolymer alone.

It is also to be noted that the lubricant compositions according to the invention retain good heat resistance under severe conditions, despite the presence of the hydrogenated styrene-isoprene copolymer which is known for its very poor heat resistance under such conditions.

EXAMPLE 3 Evaluation of the Fuel Consumption Economy Properties of Lubricant Compositions According to the Invention

The fuel consumption economy properties achieved by the use of lubricant compositions according to the invention were determined by simulation, by evaluating the coefficient of traction on a mini traction machine (MTM) according to the method described below. The tests were carried out on a PCS MTM machine in contact with an ultra-polished 10006 ball (AISI 52100 standard steel) with a diameter equal to 19.05 mm against a flat disc having the same material and surface state characteristics as the balls.

The following conditions were determined based on their being representative of the engine operation in the PRL (Piston Ring Liner) zone, the PRL zone being the zone of the engine in which most of the friction occurs and therefore the zone in which the gain in fuel efficiency can be maximized:

-   -   load on the ball of 25N,     -   drive speed of 2 m/s,     -   SRR (slide-roll ratio) of 100%, this ratio being equivalent to         the slide speed/roll speed ratio,     -   temperature of 100° C.

Thus, under these conditions, the measured coefficient of traction allows effective prediction of the gain in fuel consumption with a lubricant composition; the lower the coefficient of traction, the better the gain in fuel consumption.

Compositions L₁ to L₄ were evaluated according to the above method; the results representing the coefficient of traction of each composition are summarized in Table V.

TABLE V L₁ L₂ L₃ L₄ (compar- (compar- (inven- (inven- Compositions ative) ative) tion) tion) Coefficient of 0.039 0.036 0.034 0.035 traction

The results show that the coefficient of traction for the lubricant compositions according to the invention are lower than those obtained with a lubricant composition comprising only a hydrogenated styrene-isoprene copolymer alone or an alkoxylated fatty amine alone.

Thus, these results show that the lubricant compositions according to the invention can allow a significant gain in fuel consumption.

EXAMPLE 4 Evaluation of the Fuel Consumption Economy Properties of Lubricant Compositions According to the Invention

The fuel economy properties of the lubricant compositions according to the invention were validated by a test carried out on a test bench equipped with a MAN 5L16/24 engine. The particular characteristics of this engine have been described in the publication entitled “INNOVATOR-4C, The cutting-edge MAN B&W 5L16/24 test engine”, by D. Lancon, V. Doyen and J. Christensen, CIMAC Congress 2004, KYOTO (Paper 124).

A dedicated steady speed procedure has been developed for measuring the “fuel eco” properties of the lubricant compositions according to the following description. This procedure makes use of equipment usually found in engine test bench centres:

-   -   Rinsing the engine and lubrication circuits with the candidate         lubricant,     -   Running-in of the engine with the candidate lubricant,     -   Measurement of the consumption of distillate-type fuel oil         (Marine Diesel Oil—according to the IS08217 specification). The         measurements are repeated so as to ensure accuracy,     -   The fuel oil consumptions obtained with the candidate lubricant         are compared with those obtained when a reference lubricant is         tested under the same conditions,     -   The operating conditions of the engine are:         -   Speed: 1000 rpm,         -   Power output: 100%, 75% and 25% of the maximum power,         -   Temperature of the lubricant at the engine inlet: 68-70° C.,         -   Volume of lubricant: 2×200 litres,     -   The tests are organized according to a precise protocol which         consists of ensuring that any test carried out with a candidate         lubricant is preceded and followed by tests carried out with the         reference lubricant. This makes it possible to guarantee the         operating stability of the engine as well as the statistically         significant character of the differences in consumption measured         between lubricants,     -   In the present case, the reference lubricant is a commercial oil         for medium-speed engines with a viscosity grade of SAE40 and BN         of 30.

The reference lubricant and composition L₄ were evaluated.

The results, representing the gain in fuel consumption for the different engine loads tested, are summarized in Table VI.

TABLE VI Gain in fuel Reference L₄ consumption (%) lubricant (invention) At 100% engine load 0 0.69 At 75% engine load 0 0.79 At 25% engine load 0 1.74

The results confirm the results of Example 3, in that the lubricant composition L₄ according to the invention makes it possible to reduce the fuel consumption of a marine engine.

It is to be noted that this gain remains significant even when the engine load increases.

Thus, the above examples show that the lubricant compositions according to the invention have both good heat resistance, and therefore make it possible to increase the engine cleanliness, while significantly reducing the fuel consumption. 

1.-20. (canceled)
 21. Lubricant composition for a 4-stroke or 2-stroke marine engine, comprising: a) at least one base oil, b) at least one alkoxylated fatty amine, c) at least one hydrogenated styrene-isoprene copolymer, d) at least one detergent.
 22. Lubricant composition according to claim 21 in which the alkoxylated fatty amine is obtained from fatty acids comprising from 10 to 24 carbon atoms.
 23. Lubricant composition according to claim 21 comprising at least one alkoxylated fatty amine of formula (I)

in which: R₃ represents an alkane-di-yl group comprising from 2 to 10 carbon atoms; R₄ represents a linear or branched, saturated or unsaturated, alkyl group comprising from 12 to 22 carbon atoms; R₅ represents an alkane-di-yl group comprising from 1 to 10 carbon atoms; m represents an integer ranging from 0 to 12; n represents an integer ranging from 0 to 12; p represents an integer ranging from 0 to 12; q represents 0 or 1; the sum m+n+p is strictly greater than
 0. 24. Lubricant composition according to claim 23 in which: R₃ represents an alkane-di-yl group comprising from 2 to 4 carbon atoms; R₄ represents a linear or branched, saturated or unsaturated, alkyl group comprising from 16 to 20 carbon atoms; R₅ represents an alkane-di-yl group comprising from 2 to 4 carbon atoms; m represents 0, 1, 2, 3, 4 or 5; n represents 0, 1, 2, 3, 4 or 5; p represents 0, 1, 2, 3, 4 or 5; q represents 0 or 1; the sum m+n+p represents an integer ranging from 1 to
 15. 25. Lubricant composition according to claim 21 comprising at least one alkoxylated fatty amine of formula (Ia):

in which: R₃ represents an alkane-di-yl group comprising from 2 to 4 carbon atoms; R₄ represents a linear or branched, saturated or unsaturated, alkyl group comprising from 16 to 20 carbon atoms; m represents 0, 1 or 2; n represents 0, 1 or 2; the sum m+n represents an integer ranging from 1 to
 4. 26. Lubricant composition according to claim 21 in which the hydrogenated styrene-isoprene copolymer has a content of hydrogenated isoprene units ranging from 50% to 98% with respect to the mass of hydrogenated styrene-isoprene copolymer.
 27. Lubricant composition according to claim 21 in which the hydrogenated styrene-isoprene copolymer has a content of styrene units ranging from 2% to 50% with respect to the mass of hydrogenated styrene-isoprene copolymer.
 28. Lubricant composition according to claim 21 in which the detergent is chosen from the alkali or alkaline-earth metal salicylates or phenates, alone or in a mixture.
 29. Lubricant composition according to claim 28 in which the detergent is chosen from calcium salicylates or calcium phenates, alone or in a mixture.
 30. Lubricant composition according to claim 21 also comprising a dispersant.
 31. Lubricant composition according to claim 30 in which the dispersant is chosen from the compounds comprising at least one succinimide group.
 32. Lubricant composition according to claim 30 in which the dispersant is chosen from the borated compounds comprising at least one succinimide group.
 33. Lubricant composition according to claim 21 in which the base oil is chosen from the base oils of Group I or Group II, alone or in a mixture.
 34. Lubricant composition according to claim 21, also comprising at least one additional additive chosen from anti-wear additives, antioxidants, additional polymers improving the viscosity index, pour point improvers, anti-foaming agents, thickeners and mixtures thereof.
 35. Lubricant composition according to claim 21 having a BN determined according to the ASTM D-2896 standard, from 5 to 100 mg of KOH/g of lubricant composition.
 36. Lubricant composition according to claim 21 having a kinematic viscosity measured according to the ASTM D7279 standard at 100° C. comprised between 5.6 and 26.1 cSt.
 37. Lubricant composition according to claim 21 having a BN determined according to the ASTM D-2896 standard, from 7 to 80 mg of KOH/g of lubricant composition.
 38. Lubricant composition according to claim 21 having a kinematic viscosity measured according to the ASTM D7279 standard at 100° C. comprised between 9.3 and 21.9 cSt.
 39. Method for reducing the fuel consumption of 4-stroke or 2-stroke marine engines, comprising adding a lubricant composition according to claim 21 into the marine engines.
 40. Method for improving the engine cleanliness of 4-stroke or 2-stroke marine engines, comprising adding at least one alkoxylated fatty amine in a lubricant composition for 2-stroke or 4-stroke marine engines comprising at least one base oil, at least one hydrogenated styrene-isoprene copolymer and at least one detergent. 